Preheat oven to 375 degrees.

Spritz a 9x13 inch baking dish with non-stick cooking spray.

Slice chicken in half through the thickness of the breast horizontally and pound it to ½ inch thickness. (Avoid mess by placing chicken between sheets of plastic wrap or waxed paper when pounding.) 

Sprinkle chicken with salt and pepper. In the middle of the chicken add four slices of pepperoni and about 1 tablespoon shredded mozzarella.

Roll chicken, tucking the edges, and place in prepared baking dish.

Pour pizza sauce over each chicken breast.

Top with remaining mozzarella and pepperoni slices.

Bake for 30 to 40 minutes (depending on the thickness of the chicken breast) or until an instant thermometer reads 165 degrees.